Like a cosmic sonogram, new images showcase an infant world growing in the planetary womb that encircles a young star. This is the first time researchers have observed a young planet actively feeding from the disk of gas in which it lives.
Light from hydrogen gas swirling around the planet gave the baby world away, researchers report November 18 in Nature. The glowing hydrogen is baked to about 10,000 degrees Celsius, nearly two times as hot as the surface of our sun. The only way to get the hydrogen that hot is if it is falling onto a fledgling planet no more than 10 times as massive as Jupiter, Stephanie Sallum, an astronomy graduate student at the University of Arizona in Tucson, and colleagues report.
Other researchers spied the young planet in 2009 and 2010 as a spot of infrared light orbiting the 2-million-year old star LkCa 15, which sits in the constellation Taurus. The infrared glow that they saw probably comes from warm dust encircling the new world.
Superheated hydrogen implies that the planet has not yet finished forming. Two other planets in the system show no signs of glowing hydrogen, which could mean they’ve finished forming, are not sucking down hydrogen as aggressively or are partially masked by intervening clouds of dust.
This composite image shows the feeding planet (blue, green and red blob) sitting within a clearing in the disk (gray) that surrounds the star (which is not visible). Another planet shows up in green. Hydrogen gas shows up in blue; red and green represent other infrared wavelengths.